Benign hyperplasia of the prostate causing bladder outlet obstruction is one of the most common maladies afflicting older men, but little is known concerning its pathogenesis. There is considerable histologic diversity in the composition of hyperplastic tissue which may indicate individual patient differences in the etiology or pathogenesis of BPH, with some cases comprised primarily of stroma, and other cases containing mostly glandular epithelium and lumenal volume. Using immunohistochemistry to specifically identify the components of the tissue and quantitative morphometric techniques we will correlate the amount of each of the major tissue components with clinical factors including patient age and duration and severity of symptoms. Using specific antibodies against proteins expressed only during the mitotic cycle we can determine the correlation of proliferative indices to tissue histology and patient symptoms. The presence and distribution of hormone receptors (estrogen, progesterone, and androgen) and certain growth factors and their receptors will also be determined and quantified. Also, we will be able to determine the effects of various treatment modalities including anti-androgen therapy, alpha-adrenergic blockade, and transurethral incision of the prostate on the tissue components and proliferative indices in patients.